Question

数学里的和差化积和积化和差,和三角万能公式是什么?

Answer 1

sin(a+b)=sinacosb+cosasinb

sin(a-b)=sinacosb-cosasinb

cos(a+b)=cosacosb-sinasinb

cos(a-b)=cosacosb+sinasinb

sinacosb=[sin(a+b)+sin(a-b)]/2

cosasinb=[sin(a+b)-sin(a-b)]/2

cosacosb=[cos(a+b)+cos(a-b)]/2

sinasinb=[cos(a-b)-cos(a+b)]/2